Generally, coordinatively unsaturated metal sites are the locations where water or organic solvents are removed and thus organic metal compounds can form covalent or coordinate bonds.
A porous organic-inorganic hybrid material, is defined as a porous organic-inorganic polymer compound, formed by bonding an organic ligand with a central metal ion, and it is a crystalline compound which includes both organic building blocks and inorganic substances in its backbone structure and has a molecular-sized or a nano-sized pore structure. A porous organic-inorganic hybrid material is a broadly defined term, and generally refers to as a porous coordination polymer (Angew. Chem. Intl. Ed., 43, 2334. 2004), and also refers to as a metal-organic framework (Chem. Soc. Rev., 32, 276, 2003). Research into these materials has been newly advanced through the combination of the molecular engineering and material science. Furthermore, these materials have a large surface area, and molecular-sized or nano-sized pores, and can thus be used for adsorbents, gas storage materials, sensors, membranes, functional thin films, catalysts, catalytic supports, and the like. Accordingly, in recent years, research into these materials has been actively conducted.
An organic-inorganic mesoporous hybrid material is defined as an ordered molecular structure having a mesopore distribution in the range of 2 to 50 nm which is substituted with dissimilar metals, and thus has a coordinatively unsaturated metal sites. It was reported (Chem. Rev. 97, 2373, 1997) that the organic-inorganic hybrid mesoporous material can be widely applied to catalysts, catalytic supports, adsorbents and functional materials.
The general surface functionalizing methods for imparting applicability to the organic-inorganic mesoporous material having a large surface area, were reported in a research paper (Curr. Opin. Solid State Mater. Sci. 3, 71, 1998, Chem. Lett. 6, 624, 2000). The method involves bonding on the surface of a porous organic-inorganic hybrid material or mesoporous material by the covalent bond between an organic metal compound, for example, organic silaneand a previously-prepared hydroxide group (—OH) of the surface of it. In addition to the said method, a method of directly functionalizing the surface of a hybrid material by mixing an organic silane compound with a precursor of the mesoporous material was reported (J. Mater. Chem. 16, 1125, 2006).—Si—OH+RxM(OR)4−x(1≦x≦3)→—Si—O-M(OR)3−xRx+ROH  (Reaction Equation 1)
However, methods of selectively functionalizing the coordinatively unsaturated metal sites of the porous organic-inorganic hybrid material having few or no hydroxyl groups on the surface thereof, or the coordinatively unsaturated metal sites of the organic-inorganic mesoporous material substituted with dissimilar metals have not been reported yet.
Meanwhile, various heterogeneous catalytic reactions using organic-inorganic nano hybrid material itself have been reported recently (J. Mater. Chem. 16, 626, 2006). However, the heterogeneous catalytic reactions conducted by functionalizing the coordinatively unsaturated metal sites of a porous organic-inorganic hybrid material have not been reported so far.